It supports predictions that a changing climate could damage global production of coffee - the world's second most traded commodity after oil.

Wild Arabica is important for the sustainability of the coffee industry because of its genetic diversity.

Arabica coffee and Robusta coffee are the two main species used commercially, although the former provides about 70% of production.

The Arabica crops grown in the world's coffee plantations are from very limited genetic stock and are thought to lack the flexibility to cope with climate change and other threats such as pests and diseases.

The researchers from the Royal Botanic Gardens in Kew, UK, and the Environment and Coffee Forest Forum (ECFF) in Addis Ababa, Ethiopia, examined the future distribution of wild Arabica using climate modelling.

They looked at how wild Arabica might be affected under three different carbon emission scenarios and over three time intervals (2020, 2050 and 2080).

When the researchers looked at what would happen in the locations where Arabica was currently grown, the best-case outcome was a 65% reduction in suitable sites by 2080.

The worst-case outcome was a 99.7% reduction by 2080.

A different analytical approach yielded a 38% reduction as the most favourable outcome and a 90% reduction as the least favourable by 2080.

Cause for concern

Aaron Davis, head of coffee research at the Royal Botanic Gardens, said: "The extinction of Arabica coffee is a startling and worrying prospect. However, the objective of the study was not to provide scaremonger predictions for the demise of Arabica in the wild.

"The scale of the predictions is certainly cause for concern, but should be seen more as a baseline, from which we can more fully assess what actions are required."

Image caption
Arabica accounts for 70% of commercial production

The researchers said the results should be regarded as "conservative", because the modelling does not factor in the large-scale deforestation that has occurred in the highland forests of Ethiopia and South Sudan (the natural home of Arabica coffee).

Moreover, because of the lack of suitable data, the models assumed intact natural vegetation, whereas the highland forests of Ethiopia and South Sudan are highly fragmented due to deforestation.

Ethiopia remains a big producer of the Arabica variety, but Brazil and Colombia are now the two largest countries for commercial Arabica growing.

Other factors, such as pests and diseases, changes in flowering times, and shifting bird numbers (which disperse the coffee seeds), were also not included in the modelling.

Co-author Tadesse Woldemariam Gole, from the ECFF said: "As part of a future-proofing exercise for the long-term sustainability of Arabica production it is essential that the reserves established in Ethiopia to conserve Arabica genetic resources are appropriately funded and carefully managed."